The internal combustion engine has been a mainstay in automotive, rail, shipping and other applications. In automotive applications, the engine generally takes the form of a four cycle gasoline engine using the Otto cycle with the four cycles including intake, compression, power and exhaust. In truck and larger applications, the engine is typically a four cycle Diesel engine.
Since the initial design of the four cycle internal combustion engine, there has been an ongoing effort to improve the performance characteristics of the engine. Performance can be measured in a number of ways, including power output per engine weight or combustion chamber volume, an ability to operate on lower octane fuels, the ability to operate with greater fuel efficiency and the desire to reduce the number of moving parts within the engine, thereby increasing reliability. In recent years, emphasis has also been given in the area of emissions.
In conventional internal combustion engines, the length of stroke of the piston for each cycle is constant. This design requires the volume swept by the piston in the cylinder to be equal for each stroke of the engine cycle. Ideally, the stroke length of the piston during the power stroke should be increased relative to the other cycles to maximize the work and energy output of the engine.
In the past, several attempts have been made to design a variable stroke engine. An early example is U.S. Pat. No. 1,174,801 issued to George E. Babcock on Mar. 7, 1916. In this patent, the power stroke is not maximized. The exhaust stroke is actually longer than the power stroke. The top dead center position of the piston also varies during the four cycles. In addition, the cam shaft identified by reference numeral 6 in the patent would be required to transmit all force from the piston to the crankshaft 14, requiring the cam shaft 6 to be of equal strength to crankshaft 14. U.S. Pat. No. 1,786,423 to Cady issued Dec. 30, 1930 also discloses a variable stroke internal combustion engine. In this patent the intake stroke is the longest stroke and the power or firing stroke is the shortest stroke. Again, this patent discloses an indirect connection between the piston and crankshaft.
More recently, an internal combustion engine of a rotary type has been developed and disclosed in U.S. Pat. No. 4,157,079 issued to Kristiansen on June 5, 1979 and U.S. Pat. No. Re. 30,565 issued to Kristiansen on Apr. 7, 1981. These patents disclose a rotary engine which maximizes the stroke length of the power stroke for increased power output. The rotary engine has multiple pistons and a single cylinder with the stroke of the pistons determined by an annular cam. In U.S. Pat. No. Re. 30,565, at column 2, lines 57-59, the patent suggests a cam-type crankshaft can be utilized with a conventional opposing piston engine so that the expansion stroke is longer than the compression stroke.
However, these prior art devices have not proven totally effective. A need therefore exists for an internal combustion engine design which takes advantage of an elongated combustion stroke for increased engine output with an efficient and reliable operation.